An industrial robot comprises a manipulator and control equipment, whereby the manipulator with the assistance of the control equipment carries out arbitrary operations within a working range. Usually, such a manipulator comprises a plurality of arms which support a hand, on which a tool is arranged. In the majority of robot applications, a traditional six-axis manipulator is used, which exhibits sufficient movability to carry out a wide range of operations with mostly very high accuracy. For certain applications, however, there is a need of a manipulator which has fewer degrees of freedom but which permits faster operations. Such a manipulator may be mechanically connected in such a way that the tool-carrying hand is all the time oriented in space in a predetermined manner.
From U.S. Pat. No. 4,976,582 and WO 00/29177 a manipulator is previously known by means of which a movable element in relation to a stationary element may be moved in a space with retained orientation and retained inclination. The manipulator has three arms which jointly support the movable element. Each of these arms is rotatably journalled in the stationary element around a respective first axis. The arm supports a linkage, one end of which is rotatably journalled in the outer part of the arm, allowing movement in two degrees of freedom. In its other end, the linkage supports the movable element and is journalled therein, allowing a movement in two degrees freedom.
The linkage comprises two parallel links and is arranged, together with the arm, such that one of the degrees of freedom of each end of the linkage constitutes a rotation around an axis which is parallel to the first axis of the respective arm. Irrespective of the movements of the arm or the linkage, these three axes of rotation are thus kept in parallel. In this way, the movable element will always have the same orientation and inclination in relation to the stationary element. One condition, however, is that the respective first axes of the arms form an angle with each other. This kind of industrial robot is usually referred to as parallelkinematic manipulator.
On the movable element on this kind of industrial robot, as well as in various other kinds of industrial robots, the movable element is provided with a swivel for the attachment of a tool for the manipulating. The swivel thus has an attachment device for a certain kind of tool.
In many cases the robot is applied to manipulate different kind of products requiring different kind of tools. This is the case when the products have different geometric shape. There might also be other grounds for the need to change the tool. E.g. in the food industry one product might include nuts whereas another product absolutely has to be free from nuts. If one of the products is not rotation symmetrical it is required to re-calibrate the robot when changing the tool. Alternatively the plate on which the tool is to be attached can be exchanged. This however, requires detaching the arms of the robot that carry the plate. This is complicated and time-consuming.
The object of the present invention is to overcome the above drawbacks and thus to solve the problem of achieving a cost effective operation in cases where two different kinds of tools are required.
DE 20 2005 003 748 U1 discloses a swivel for a manipulator having a certain flexibility. The swivel is built up by modules in order to allow different numbers of pneumatic drives to be connected to the swivel.